How to gauge harm to threatened steelhead was a central question in a three-way courtroom battle last week between ranchers, environmentalists and the federal government.
U.S. District Judge Ancer Haggerty heard arguments in the case Tuesday, March 30, in Portland.
The debate stems from a legal challenge against cattle grazing in Eastern Oregon's Malheur National Forest. An environmental group, the Oregon Natural Desert Association, claims the federal government violated the Endangered Species Act by permitting grazing to degrade steelhead habitat in the national forest.
A key measure of cattle grazing's impact on steelhead is bank alteration, which is basically the percentage of the streambank that's altered by hoof prints.
Ranchers on 13 allotments in the forest are expected to keep bank alteration below 10 percent to 20 percent, depending on the area, as part of the federal requirements that allow grazing.
The environmental group claims that exceeding those thresholds is equivalent to killing steelhead, an "unlawful take" that constitutes a violation of the Endangered Species Act.
Ranchers who rely on the forest to graze their cattle allege those thresholds were arbitrarily set by the federal government and aren't based on the best available science, as required by the ESA.
"There isn't a connection between bank alteration and actual death and injury to steelhead," said Elizabeth Howard, an attorney representing ranchers during oral arguments. "There isn't any evidence of that."
David Becker, an attorney for the Oregon Natural Desert Association, countered that bank alteration has been linked to increased sedimentation, higher stream temperature and damage to fish egg-laying habitat.
"Habitat damage occurred and that was enough to show take," said Becker.
The group claims past "exceedances" of the bank alteration thresholds indicate the federal government's grazing rules for the national forest haven't been properly enforced.
No further evidence is needed to prove a "take" of protected species, he said. "There are no photographs of sediment being knocked down and fish scrambling away."
Both the environmental group and the ranchers are challenging the validity of a "biological opinion" and related documents issued by the federal government in 2007, which set standards for grazing in the forest.
The Oregon Natural Desert Association claims the government delegated too much responsibility for riparian health to the ranchers, without reasonable assurances that its conservation measures would be followed.
The ranchers, meanwhile, contend that the federal government should use more accurate standards to measure the viability of steelhead habitat in the allotments.
"What we really should be evaluating is bank stability," said Howard, rather than bank alteration.
The federal agencies involved in the lawsuit - the National Marine Fisheries Service and the U.S. Forest Service - had to defend the bank alteration standard while acknowledging its limitations.
Stephen Odell, an attorney representing the federal government, disagreed with the ranchers' view that bank alteration is an arbitrary standard. It's a legitimate method that will continue to be used for measuring riparian health, he said.
When the thresholds for alteration are exceeded, the federal agencies evaluate the damage and find ways to remedy it in compliance with the Endangered Species Act, he said.
However, bank alteration is just one method for gauging impacts from grazing, Odell said. Other factors, such as stream vegetation, must also be considered, he said.
"Bank alteration itself is not sufficient to establish a take," Odell said.
The federal government is caught between two groups which claim its standards are either too lenient or too restrictive, he said.
In this situation, the court should defer to the agencies' expertise and let the federal government's decision stand, Odell said.
Oral arguments on the legal validity of the biological opinion were held March 30 in a federal district court in Portland.
Judge Haggerty said he's taking the matter under advisement and will "get a ruling out shortly."
Meanwhile, ranchers expect to turn cattle out on the allotments between May 15 and June 1.